Directory assistance call completion or "DACC" service has been deployed by a number of the local telephone operating companies (TELCO's). The DACC service enables a directory assistance caller to request and obtain automatic completion of a call to the station identified in the requested directory listing, for example by simply pressing "one" on a dual tone multifrequency telephone, such as a TOUCHTONE telephone. The directory assistance telephone system and the associated telephone network provide a completed voice grade connection between the caller's station and the station identified by the directory listing and record an additional charge, e.g. $.30, for billing on the caller's telephone bill. Set up of the connection to the destination station is faster than for manual dialing. Such automatic call completion also eliminates the need for the caller to memorize or write down the telephone number from the retrieved directory listing.
DACC eligibility screening is performed on every directory assistance call. Calls involving inter-LATA completions as well as calls from selected stations such as hotels, dormitories, etc., typically are screened out and the caller is not offered DACC. In addition, present systems screen out calls from cellular telephone users. Present systems do not offer the DACC service to cellular customers because with current network arrangements it is not possible to bill the individual cellular station subscriber for the DACC related charges, as discussed below.
A mobile telephone switching office or "MTSO" is owned and operated by the cellular carrier. The MTSO provides a switched connection point between the network operated by the cellular carrier and the landline telephone network. In existing cellular systems, the Mobile Telephone Switching Office (MTSO) receives dialing information from the mobile telephone and establishes a trunk connection to a local switching office of the landline telephone network. The MTSO forwards pertinent data to the local office, including the destination telephone number, and the local office uses that information to complete the landline portion of the call through the telephone network to the destination station.
The cellular system treats directory assistance calls in a similar manner. The cellular telephone user dials 411, 555-1212, or area code plus 555-1212, and the MTSO establishes a trunk connection to the local switching office. The MTSO forwards the pertinent data to the local office, including the information service number, e.g., 555-1212. The call is routed through the landline telephone network to an Operator Service System (OSS) and connected to an available operator position terminal.
The cellular carrier, through programming in the MTSO, knows that the cellular subscriber has made a directory assistance call and the air time for each such call; and the cellular carrier can bill accordingly. Once the call reaches the OSS, however, the MTSO is no longer expecting any dialed digit data from the cellular telephone. Thus the MTSO does not have a DTMF receptor monitoring the call and will not recognize the dialing of a "1" or the like to request call completion via a DACC service. The cellular carrier therefore would not know that the subscriber requested call completion and could not bill for servicing the request.
Under present procedures, the telephone network also can not identify the particular cellular subscriber who might initiate a directory assistance call completion request. In many systems presently in use, the data forwarded from the MTSO to the OSS for a call from a cellular telephone does not include any form of automatic number identification data (ANI) corresponding to the actual cellular station which initiated, the call. Instead, MTSO's in such systems forward no ANI at all or forward only a number corresponding to the MTSO for all directory assistance calls. The TELCO bills the cellular carrier for directory assistance calls on a per call basis, and the cellular carrier passes the charges on to individual subscribers who made directory assistance calls during a given billing period, but there is no effective way to bill for call completion services if provided to a cellular customer.
It would be possible to bill directory assistance call completion charges to the cellular carrier, but because there is no data stored by either the cellular carrier or the TELCO, there is no way to bill the charges to each cellular caller who actually requested such call completion. The cellular carrier would have to average any additional charges incurred as a result of the call completion into cellular system charges for directory assistance calls or into the charges for all cellular calls. Cellular carriers have been unwilling to bill call completion on such an average basis, and consequently call completion has not been offered to cellular telephone service subscribers.
It can be seen from the above analysis that directory assistance call completion is a desirable service which existing call processing procedures and existing communications systems can not offer to cellular telephone subscribers.